Memory residence can buy both functionality and performance for a database management system. In this paper, we present a description and a benchmark of an experimental implementation of a Main Memory Database System (MMDBS) that was designed to support complex interactive queries. We describe and evaluate the main memory database structures and query processing algorithms implemented in this prototype. Our measurements and analysis, focused on aggregates and joins, include both memory requirements and response time, since there is a clear trade-off between space and time in the design of a MMDBS. In contrast to conventional Disk-based Database Systems (DDBS's), we found that an MMDBS can efficiently execute complex relational queries. We identify strategies that exploit memory residence effectively. We also identified a number of performance problems related to query optimization in main memory and memory management for MMDBS's.

Office-by-Example (OBE) is an integrated office information system that has been under development at IBM Research. OBE, an extension of Query-by-Example, supports various office features such as database tables, word processing, electronic mail, graphics, images, and so forth. These seemingly heterogeneous features are integrated through a language feature called example elements . Applications involving example elements are processed by the database manager, an integrated part of the OBE system. In this paper we describe the facilities and architecture of the OBE system and discuss the techniques for integrating heterogeneous objects.